[jack_bm]

Originally Posted by Sonofswin

Alright, so basically the ecu adjusts various aspects of the bike (air/fuel ratio, ignition timing) according to the O2 sensor readings and a few other things (air intake temp, coolant temp, etc.) However, the stock ecu can only adjust so much, so if you make large changes in your intake/exhaust systems, it can't compensate enough.

Then, you'll need something like a power commander to maintain performance as well as to keep your bike in good condition. (Running it too lean all the time isn't going to be good for the engine.) The power commander simply adjusts the adjustments of the original ecu by overriding (disabling/replacing?) the O2 sensor and doing what you tell it to at a given throttle position and RPM. (Called Mapping) Thereby giving you the best performance for your set-up.

Pros: Even on a stock bike (Or one with a slightly modified intake/exhaust system) you'll get better performance and response with a smoother ride by using the stock map. (See the 1st post in the Jetting Database thread for a good explanation of why stock bike are as they are.)

Cons: They're expensive. AND, there aren't many maps out there, so you may have to pay someone to map your bike for you according to the system/conditions you ride in. (Also expensive.)

In conclusion: Do you need one? Probably not if you just add a slip-on. But I'd recommend you keep an eye on your plugs to see how your engine feels about it.

What do you mean plugs? Spark plugs?